As a result we're building device builds approximately 40% faster than
before.

Between June 12th and June 17th, 50% of our successful JB emulator builds
on mozilla-inbound finished in 97 minutes or less. Using unified sources
for these builds reduced the 50th percentile of build times down to 60
minutes (from June 19th to June 24th).

To mitigate the risks of changes landing that break non-unified builds,
we're also doing periodic non-unified builds for these devices.

As usual, all our work here was done in the open. If you're interested,
read along in bug 950676, and bug 942167.